1. Field of the Invention
An object of the present invention is an electronic connection device that can be used, in particular, to connect a peripheral unit to a central processing unit in a data-processing system.
2. Description of the Prior Art
There are known electronic connection devices which essentially include an arrangement of switches that can be activated by hand. For example there is one arrangement of switches which, used with a parallel type address bus, (i.e. a bus that comprises a certain number, e.g. eight, of conductive wires), has a switch in parallel with each of the conductive wires of the bus. These switches may have two positions: open or closed. An address, namely a logic state, is sent on the address bus. It is compared with the arrangement of switches. If this arrangement is configured in the same way as the address to be sent, the connection device produces a validation signal that permits the operation of the peripheral unit, under the control of the central processing unit, because this unit has been recognized as being the peripheral unit for which the instructions from this central processing unit are intended. In a computer system, for example with micro-computers, a peripheral unit such as this may be a printer, externally connected to the micro-computer, or it may be a unit internally connected to the micro-computer, for example a modem or a communications card with a display screen or with a digital optic disk reader.
Switches such as these are generally of the electromechanical type. They have drawbacks. Firstly, they have to be manipulated by hand, but their small size often makes them difficult to handle. Furthermore, to make it possible to reach them, it is necessary to make windows providing access to these microswitches in the rear or front faces of the machines containing electronic cards to which these microswitches are fixed. These access windows impose troublesome constraints on the manufacturing process. In other installations, the electronic cards containing these switches that play the role of access means to the peripherals are connected by their edges to a parent card. These cards are very close to one another. In this case, to make it possible to manipulate these switches, the electronic card bearing them has to be unplugged from the parent card after the electrical supply has been cut off, and then this electronic card has to be plugged in again after the manipulation. The connectors of the communications cards on the parent card are not easy to disconnect. They are not designed to be put under strain too often. Their reliability does not last beyond about a hundred operations of insertion and removal. Another drawback of this technique is that it also calls for the prior removal of the cover of the machine.
Moreover, the micro-switches themselves are mechanically fragile. First of all, they are very sensitive to vibrations: they are thus liable to change their state depending on shocks received. In this case, it is difficult for them to overcome validation constraints of a military type. In addition, the electromechanical nature of the contacts set up make them sensitive to dust and to the oxidation of the contacts, and entails a very complicated manufacturing technology. This manufacturing technology itself induces high implementation costs.